Semiconductor Component

ABSTRACT

A semiconductor component may include a semiconductor layer which has a front side and a back side, a first terminal electrode on the front side, a second terminal electrode on the back side, a first dopant region of a first conduction type on the front side, which is electrically connected to one of the terminal electrodes, a second dopant region of a second conduction type in the semiconductor layer, which is electrically connected to the other terminal electrode, a pn junction being formed between the first and second dopant regions, a dielectric layer on the back side between the semiconductor layer and the second terminal electrode, and the dielectric layer having an opening through which an electrical connection between the second terminal electrode and the first or second dopant region is passed.

RELATED APPLICATIONS

This Application claims priority of German Patent Application No.102010020884.1, which was filed on May 18, 2010. The entire contents ofthe German Patent Application are hereby incorporated herein byreference.

FIELD OF THE INVENTION

Exemplary embodiments of the present invention may relate to asemiconductor component having one terminal electrode on a front side ofa semiconductor layer and having a further terminal electrode on theback side of the semiconductor layer, and a pn junction formed in thesemiconductor layer.

BACKGROUND

Avoiding or suppressing stray properties is often the goal ofdevelopment work for semiconductor components. Particularly in the caseof power semiconductor components, stray capacitances are oftenundesired.

In order to avoid for example undesired gate-drain capacitances, alateral DMOS may be produced which achieves very good control of thegate-drain overlap region, and therefore the gate-drain capacitance, byway of self-aligned implantation of the LDD region at the gateelectrode. The drain or the source is connected to the back side by wayof a sinker. This leads to an increased output capacitance which resultsfrom the body region at source potential forming a pn junction bothvertically with the drain sinker and laterally with the substrate atdrain potential.

SUMMARY

Embodiments of the invention relate in general to a semiconductorcomponent, in particular a power semiconductor component, comprising asemiconductor layer which has a front side and an opposite back side, afirst terminal electrode on the front side of the semiconductor layer, asecond terminal electrode on the back side of the semiconductor layer, afirst dopant region of a first conduction type on the front side in thesemiconductor layer, which is electrically connected to one of theterminal electrodes, a second dopant region of a second conduction typein the semiconductor layer, which is electrically connected to the otherterminal electrode, a pn junction being formed between the first andsecond dopant regions, and a dielectric layer on the back side of thesemiconductor layer between the semiconductor layer and the secondterminal electrode, the dielectric layer having an opening through whichan electrical connection between the second terminal electrode and thefirst or second dopant region is passed.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows in a schematic cross-sectional view an embodiment of asemiconductor component having a dielectric layer between a pn junctionand a backside terminal electrode.

FIG. 2 shows in a schematic cross-sectional view an embodiment of alateral MOS power semiconductor transistor having a backside drainterminal.

FIG. 3 shows in a schematic cross-sectional view an embodiment of alateral MOS power semiconductor transistor having a “source-down”structure.

FIG. 4 shows in a schematic cross-sectional view an embodiment of alateral MOS power semiconductor transistor having a “source-down”structure and gate screening.

FIG. 5 shows in a schematic cross-sectional view an embodiment of alateral MOS power semiconductor transistor having a backside drainterminal and a buried p-plate under the channel.

FIG. 6 shows in a schematic cross-sectional view another embodiment of alateral MOS power semiconductor transistor having a backside drainterminal.

DETAILED DESCRIPTION

Exemplary embodiments of the invention will be explained in more detailbelow with reference to the appended figures. The invention is nothowever restricted to the embodiments specifically described, but may bemodified and adapted in a suitable way. It is within the scope of theinvention to combine individual features and feature combinations of oneembodiment suitably with features and feature combinations of anotherembodiment, in order to obtain other embodiments according to theinvention.

Before the exemplary embodiments of the present invention are explainedin more detail below with reference to the figures, it will be pointedout that elements which are the same in the figures are provided withidentical or similar references and repeated description of theseelements is omitted. Furthermore, the figures are not necessarily trueto scale; rather, the focus is on explaining the basic principle.

FIG. 1 shows a semiconductor component in a schematic cross-sectionalview. The exemplary embodiment comprises a semiconductor layer 10 havinga front side 11 and back side 12. Here and in what follows, the frontside 11 is intended to mean the side of the semiconductor layer 10 onwhich implantations or diffusions of dopants into the semiconductorlayer 10 are carried out in order to form active component structures,or on which a possible epitaxial layer is grown. The back side 12 refersto the opposite side of the semiconductor layer 10 from the front side11. The semiconductor layer 10 may consist of any known semiconductormaterial. On the front side 11 of the semiconductor layer 10, a firstterminal electrode 13 is applied which is electrically connected to afirst dopant region 15 of a first conduction type. The p- or n-dopedfirst dopant region 15 is arranged on the front side 11 in thesemiconductor layer 10, the first terminal electrode 13 being arrangeddirectly on the surface of the first dopant region. On the back side 12of the semiconductor layer 10, a second terminal electrode 14 isarranged which is electrically connected to a second dopant region 16 ofa second conduction type, complementary to the first dopant region 15.The second dopant region 16 likewise lies in the semiconductor layer 10,the second dopant region forming either a part of the semiconductorlayer 10 or the entire remainder of the semiconductor layer 10 apartfrom the first dopant region. Between the first dopant region 15 and thesecond dopant region 16, a pn junction 17 is formed in the semiconductorlayer 10. On the back side 12 of the semiconductor layer 10, adielectric layer 18 is arranged between the semiconductor layer 10 andthe second terminal electrode 14, the dielectric layer 18 having anopening 19 through which an electrical connection 20 between the secondterminal electrode 14 and the second dopant region 16 is passed. Theelectrical connection 20 in the present exemplary embodiment is formedby a part of the semiconductor layer 10 continued in the opening 19 asfar as the second terminal electrode 14.

FIG. 2 shows a possible alternative embodiment of a semiconductorcomponent. The semiconductor component constitutes a lateral MOS powertransistor, which has a backside drain terminal. In FIG. 2, a pluralityof identical semiconductor components of this type are shown next to oneanother in a semiconductor layer 10. Each of these lateral MOS powertransistors has, in the semiconductor layer 10, a first dopant region 15of a first conduction type as a body region, a second dopant region 16of a second conduction type as a drift section and a third dopant region22 of a second conduction type as a source region, one pn junction 17being formed between the drift section and the body region and a furtherpn junction 23 being formed between the body region and the sourceregion. The two pn junctions 17 and 23 are respectively arranged as faras a frontside surface of the semiconductor layer 10. Over a channelregion 15 a in the body region 15, between the two pn junctions 17 and23, a control electrode 25 is applied on the front side 11 of thesemiconductor layer 10 so that, when a control voltage is applied to thecontrol electrode, an electrically conductive channel can be formedinside the channel region along the surface of the semiconductor layer10 between the source region 22 and the drift section 16. The controlelectrode 25 (gate electrode) is separated from the channel region 15 aby a thin gate dielectric. In one embodiment, the control electrode 25may be composed of a plurality of electrically conductive layers.

The source region 22, introduced for example by diffusion of a dopant onthe front side 11 of the semiconductor layer 10 into the semiconductorlayer 10, and the body region 15 are electrically connected together inthis exemplary embodiment to the terminal electrode 13 on the front side11 of the semiconductor layer 10. Both the source region 22 and the bodyregion 15 are thus at source potential. The terminal electrode 13 iselectrically insulated from the semiconductor layer 10 and the gateelectrode 25 in wide parts by way of a dielectric layer 26. Only above aterminal zone 29 in the semiconductor layer 10, which is provided inorder to connect the source region 22 and the body region 15 to theterminal electrode 13 and which in general is more heavily doped thanthe semiconductor regions to be connected, is an opening 27 providedinside the dielectric layer 26, through which an electrical connectionis established between the terminal electrode 13 and the semiconductorlayer 10.

The second terminal electrode 14, for the drain terminal of the MOSpower transistor, lies on the back side 12 of the semiconductor layer10. Between the semiconductor layer 10 and the terminal electrode 14lies the dielectric layer 18 and additionally, in this exemplaryembodiment, a further doped semiconductor region 14 a. The further dopedsemiconductor region 14 a has in general a low electrical resistance, inorder to establish a good electrical connection between the driftsection 16 and the terminal electrode 14. For this reason, thesemiconductor region 14 a should have a dopant concentration of morethan 5×1017 cm-3.

As can be seen in FIG. 2, in the lateral MOS power transistor the flowof current is provided along the front side 11 surface of thesemiconductor layer 10 from the source region 22 through the channelregion 15 a and along the drift section 16 to a contact region 24. Thecontact region 24 is arranged on the front side 11 of the semiconductorlayer 10 within the drift section 16. The contact region 24 is used forelectrical contact between a low-impedance electrical connection line21, which extends from the front side 11 to the back side 12 of thesemiconductor layer 10, and the drift section 16. The electricalconnection line 21 is electrically connected through the opening 19inside the dielectric layer 18 either directly to the terminal electrode14 or, as in the present case, to the further doped semiconductor region14 a, and therefore constitutes a part of a low-impedance electricalconduction path from the front side 11 of the semiconductor layer 10 tothe backside terminal electrode 14. The electrical connection line 21 iseither a heavily doped semiconductor material of the same conductiontype as the drift section and introduced for example in thepolycrystalline state, or another highly conductive material, forexample a metal.

In order to avoid stray capacitances, a dielectric layer 18 a isadvantageously formed at least partially outside the contact region 24between the body region 15, or the source region 22, and thelow-impedance electrical connection line 21. In the exemplary embodimentof a lateral MOS power transistor represented in FIG. 2, a furtheropening 28 is optionally furthermore provided in the dielectric layer 18on the back side 12 of the semiconductor layer 10. This further opening28 is provided below the terminal zone 29, i.e. on the shortest pathbetween the terminal zone 29 and the backside terminal electrode 14.Through this further opening 28 in the dielectric layer 18, anelectrical connection is formed from the drift section 16 to the secondterminal electrode 14 or, if present, to the further semiconductorregion 14 a. The opening 28 may be filled with the semiconductormaterial of the drift section 16 in order to establish this electricalconnection. A breakdown point for a possibly occurring avalanchebreakdown within the component can be defined by this opening. It isparticularly advantageous for the further opening 28 not to lie underthe channel region 15 a. The injection of so-called “hot” chargecarriers into the gate dielectric in the event of an avalanche breakdownis therefore prevented.

FIG. 3 represents another possible embodiment of a lateral MOSsemiconductor power transistor. As in FIG. 2, a plurality of identicalMOS power transistors are shown next to one another in FIG. 3. Each MOSpower transistor is formed in a common semiconductor layer 10 and has afirst dopant region 15 of a first conduction type as a body region, asecond dopant region 16 of a second conduction type as a drift sectionand a third dopant region 22 of a second conduction type as a sourceregion. In contrast to the exemplary embodiment of FIG. 2, an MOSsemiconductor transistor in FIG. 3 is formed with a so-called“source-down structure.” That is to say the source terminal of the MOSsemiconductor transistor lies on the back side 12 of the semiconductorlayer 10 while the drain terminal is applied on the front side 11. Therespective terminal electrodes 13 and 14 for the source and drain areseparated from the semiconductor layer 10 by the dielectric layers 18and 26. The electrical connection 20 between the source region 22 on thefront side 11 and the source terminal electrode 14 on the back side 12is made by way of an electrical connection line 21 from the terminalelectrode 14 through an opening 19 in the backside dielectric layer 18to the source region 22 on the front side 11. The drain contact region24, drift section 16, body region 15 and source region 22 are arrangedon the front side of the semiconductor layer 10 in the lateraldirection. The back side 12 of the semiconductor layer 10 is weaklyp-doped. The drain contact region 24 is electrically connected to thedrain terminal electrode 13 on the front side 11 through an opening 27in the front side dielectric layer 26.

FIG. 4 shows an exemplary embodiment of a “source-down” transistoraccording to FIG. 3 in which screening 31, including for exampletitanium/titanium nitride and connected to the source region 22, isarranged over the gate electrode 25. The screening 31 lies for example,as represented, between the gate electrode 25 and the source terminalelectrode 13, inside the dielectric layer 26.

FIG. 5 represents another exemplary embodiment of a lateral MOS powertransistor with a back side drain terminal, as has already beenexplained with reference to FIG. 2. In contrast to the exemplaryembodiment of FIG. 2, the present variant does not however have afurther opening 28 in the back side dielectric layer 18. Instead, afourth dopant region 32 of the first conduction type, for example ap-conductive region, which is connected to the source terminal electrode13, is also arranged below the body region 15 in the second dopantregion 16. This fourth dopant region 32 extends below the body region 15laterally beyond the edges of the body region 15 in the direction of thedrain contact region 24. A heavier dopant concentration of this fourthdopant region 32, compared with the body region 15, causes adisplacement of a possibly occurring avalanche breakdown away from thechannel region 15 a towards the fourth dopant region 32. The breakdownthus takes place on the edge of the fourth dopant region 32 lyingclosest to the drain contact region 24.

FIG. 6 shows another alternative embodiment of a lateral MOS powertransistor which has a back side drain terminal, as also alreadyrepresented in FIG. 2.

In contrast to the embodiment of FIG. 2, in the exemplary embodiment ofFIG. 6 the body region 15 of the MOS power transistor is formed by thesemiconductor material of the original, for example epitaxially producedsemiconductor layer 10, whereas the drift section 16 on the front side11 of the semiconductor layer 10 is formed by diffusion of a dopant of aconduction type complementary to the body region 15 into thesemiconductor layer 10.

In the exemplary embodiment shown, a dopant region 35 with doping of thesame conduction type as the contact region 24 and the drift section 16is formed in the semiconductor layer 10, in the opening 28 on the backside 12 of the semiconductor layer 10, for electrical connection betweenthe semiconductor layer 10 and the second terminal electrode 14.

Owing to the dielectric layer shown in the embodiments, for example, thestray capacitance of the pn junction is reduced because the space chargezone built up in the off state when applying an off-state voltage to thepn junction is limited by the dielectric layer, i.e. there is a greatervoltage drop across the dielectric layer than in the semiconductorlayer. Preferably, the dielectric layer is therefore placed as close aspossible to the pn junction in order to restrict the extent of the spacecharge zone as much as possible, i.e. achieve as high as possible avoltage drop inside the dielectric layer, so as to reduce the straycapacitance. Typical distances from the dielectric layer to the pnjunction are accordingly less than the extent of a space charge zonewith an applied off-state voltage in the semiconductor material on oneside of the pn junction. In order to be able to carry a load currentthrough the semiconductor component in spite of this, a current paththrough the dielectric layer must be opened. This current path leadsthrough the opening in the dielectric layer, so that the load currentcan be carried from one side of the semiconductor component to theopposite side.

In a refinement of the semiconductor component, the electricalconnection through the opening in the dielectric layer is formed by wayof a low-impedance electrical connection line. Owing to the lowimpedance, good electrical conduction of the current through thesemiconductor component can be achieved. Electrical power losses canthereby be avoided.

In one exemplary embodiment, the low-impedance electrical connectionline extends from the front side to the back side of the semiconductorlayer. The semiconductor component can therefore be formed essentiallyon the front side of the semiconductor layer while the current cannevertheless be delivered or taken off on the back side of thesemiconductor layer. For example, lateral MOS transistors can be formedby configuration on the front side. Owing to the lateral alignment, moreaccurate or reduced overlap regions of the semiconductor component, andtherefore lower stray capacitances, can be set intrinsically byproduction owing to “self-aligned” implantations on the front side ofthe semiconductor layer.

In another embodiment, the semiconductor component has a third dopantregion of a second conduction type in the semiconductor layer, a furtherpn junction being formed between the third dopant region and the firstdopant region, and the third dopant region being electrically connectedto the same terminal electrode as the second dopant region. An MOStransistor can therefore be produced as a semiconductor component.

In one embodiment, the second dopant region is electrically connected tothe first terminal electrode and the first and third dopant regions areelectrically connected to the second terminal electrode. A “source-down”component can thereby be produced.

According to another embodiment, the second dopant region iselectrically connected to the second terminal electrode and the firstand third dopant regions are electrically connected to the firstterminal electrode. This is the normal terminal configuration of a powertransistor having a backside drain terminal and a frontside sourceterminal.

According to one exemplary embodiment, the first dopant region has acontact region on the front side of the semiconductor layer for anelectrical contact with the low-impedance electrical connection line,and a dielectric layer is formed at least partially outside the contactregion between the first dopant region and the low-impedance electricalconnection line. In this way, the stray drain-source capacitance canadditionally be reduced.

In a refinement of the semiconductor component, a further dielectriclayer is arranged between the semiconductor layer and the first terminalelectrode, the further dielectric layer having an opening through whichan electrical connection between the first terminal electrode and thefirst or second dopant region is passed. This allows problem-freeformation of the terminal electrode over a large area on the front sideof the semiconductor layer.

In one exemplary embodiment of the semiconductor component, a controlelectrode is applied on the front side of the semiconductor layer over achannel region in the first dopant region so that an electricallyconductive channel can be formed in the channel region between thesecond dopant region and the third dopant region when a control voltageis applied to the control electrode.

According to another exemplary embodiment of the semiconductorcomponent, the third dopant region has a terminal zone for the firstterminal electrode, and a further opening with an electrical connectionof the semiconductor layer to the second terminal electrode is formed inthe dielectric layer on the back side of the semiconductor layer belowthe terminal zone. An improved breakdown behaviour of the semiconductorcomponent in the event of an avalanche breakdown can thereby beachieved. In particular, by suitable placement of the further opening insuch a way that the further opening in the dielectric layer on the backside of the semiconductor layer does not lie under the channel region,the breakdown point of the semiconductor component can be set so thatthe injection of so-called “hot” charge carriers, i.e. highly energeticcharge carriers, into the gate oxide of an MOS transistor is prevented.

In one embodiment of the semiconductor component, a further dopedsemiconductor region is arranged between the dielectric layer and thesecond terminal electrode. This has manufacturing technology advantagesbecause the growth of an epitaxial semiconductor layer is made possibleby the preferably monocrystalline doped semiconductor region. It ispossible to produce the structure of the semiconductor component inparticular by lateral epitaxial growth of a dielectric layer produced onthe doped semiconductor region.

In one embodiment, at least the dielectric layer on the back side has alower dielectric constant k than the semiconductor material of thesemiconductor layer. A reduction of the stray capacitances can therebybe achieved. The dielectric layer is, for example, formed at leastpartially as an oxide layer or as a cavity.

1. Lateral MOS power transistor, comprising a semiconductor layer whichhas a front side and an opposite back side, a source electrode on thefront side of the semiconductor layer, a drain electrode on the backside of the semiconductor layer, a first dopant region of a firstconduction type on the front side in the semiconductor layer, which iselectrically connected to the source electrode, a second dopant regionof a second conduction type in the semiconductor layer, which iselectrically connected to the drain electrode, a pn junction beingformed between the first and second dopant regions, and a dielectriclayer on the back side of the semiconductor layer between thesemiconductor layer and the drain electrode, the dielectric layer havingan opening through which an electrical connection between the drainelectrode and the second dopant region is passed.
 2. Lateral MOS powertransistor according to claim 1, wherein the electrical connectionthrough the opening in the dielectric layer is formed by means of alow-impedance electrical connection line.
 3. Lateral MOS powertransistor according to claim 2, wherein the low-impedance electricalconnection line extends from the front side to the back side of thesemiconductor layer.
 4. Lateral MOS power transistor according to claim1, having a third dopant region of a second conduction type in thesemiconductor layer, a further pn junction being formed between thethird dopant region and the first dopant region, and the third dopantregion being electrically connected to the source electrode.
 5. LateralMOS power transistor according to claim 2, wherein the second dopantregion has a contact region on the front side of the semiconductor layerfor an electrical contact with the low-impedance electrical connectionline, and a dielectric layer is formed at least partially outside thecontact region between the second dopant region and the low-impedanceelectrical connection line.
 6. Lateral MOS power transistor according toclaim 1, wherein a further dielectric layer is arranged between thesemiconductor layer and the source electrode, the further dielectriclayer having an opening through which an electrical connection betweenthe source electrode and the first dopant region is passed.
 7. LateralMOS power transistor according to claim 4, wherein a control electrodeis applied on the front side of the semiconductor layer over a channelregion in the first dopant region so that an electrically conductivechannel can be formed in the channel region between the second dopantregion and the third dopant region when a control voltage is applied tothe control electrode.
 8. Lateral MOS power transistor according toclaim 4, wherein the third dopant region has a terminal zone for thesource electrode, and a further opening with an electrical connection ofthe semiconductor layer to the second terminal electrode is formed inthe dielectric layer on the back side of the semiconductor layer belowthe terminal zone.
 9. Lateral MOS power transistor according to claim 8,wherein the further opening in the dielectric layer on the back side ofthe semiconductor layer does not lie under the channel region. 10.Lateral MOS power transistor according to claim 1, wherein a furtherdoped semiconductor region is arranged between the dielectric layer andthe second terminal electrode.
 11. Lateral MOS power transistoraccording to claim 1, wherein at least the dielectric layer on the backside has a lower dielectric constant k than the semiconductor materialof the semiconductor layer.
 12. Lateral MOS power transistor accordingto claim 1, wherein the dielectric layer at least partially comprises acavity.
 13. Lateral MOS power transistor, comprising a semiconductorlayer which has a front side and an opposite back side, a drainelectrode on the front side of the semiconductor layer, a sourceelectrode on the back side of the semiconductor layer, a first dopantregion of a first conduction type on the front side in the semiconductorlayer, which is electrically connected to the source electrode, a seconddopant region of a second conduction type in the semiconductor layer,which is electrically connected to the drain electrode, a pn junctionbeing formed between the first and second dopant regions, and adielectric layer on the back side of the semiconductor layer between thesemiconductor layer and the source electrode, the dielectric layerhaving an opening through which an electrical connection between thesource electrode and the first dopant region is passed.
 14. Lateral MOSpower transistor according to claim 13, wherein the electricalconnection through the opening in the dielectric layer is formed bymeans of a low-impedance electrical connection line.
 15. Lateral MOSpower transistor according to claim 13, having a third dopant region ofa second conduction type in the semiconductor layer, a further pnjunction being formed between the third dopant region and the firstdopant region, and the third dopant region being electrically connectedto the source electrode.
 16. Lateral MOS power transistor according toclaim 14, wherein the low-impedance electrical connection line extendsfrom the front side to the back side of the semiconductor layer. 17.Lateral MOS power transistor according to claim 13, wherein a furtherdielectric layer is arranged between the semiconductor layer and thedrain electrode, the further dielectric layer having an opening throughwhich an electrical connection between the drain electrode and thesecond dopant region is passed.
 18. Lateral MOS power transistoraccording to claim 4, wherein a control electrode is applied on thefront side of the semiconductor layer over a channel region in the firstdopant region so that an electrically conductive channel can be formedin the channel region between the second dopant region and the thirddopant region when a control voltage is applied to the controlelectrode.
 19. Lateral MOS power transistor according to claim 1,wherein at least the dielectric layer on the back side has a lowerdielectric constant k than the semiconductor material of thesemiconductor layer.
 20. Lateral MOS power transistor according to claim1, wherein the dielectric layer at least partially comprises a cavity.21. Semiconductor component, comprising a semiconductor layer which hasa front side and an opposite back side, a first terminal electrode onthe front side of the semiconductor layer, a second terminal electrodeon the back side of the semiconductor layer, a first dopant region of afirst conduction type on the front side in the semiconductor layer,which is electrically connected to one of the terminal electrodes, asecond dopant region of a second conduction type in the semiconductorlayer, which is electrically connected to the other terminal electrode,a pn junction being formed between the first and second dopant regions,a dielectric layer on the back side of the semiconductor layer betweenthe semiconductor layer and the second terminal electrode, thedielectric layer having an opening through which an electricalconnection between the second terminal electrode and the first or seconddopant region is passed.